PIC16LC773-04SLASHSP datasheet(117/200 Pages) MICROCHIP

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PIC16C77X

Advance Information

DS30275A-page 117

11.0

ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The analog-to-digital (A/D) converter module has six

inputs for the PIC16C773 and ten for the PIC16C774.

The analog-to-digital converter (A/D) allows conver-

sion of an analog input signal to a corresponding

12-bit digital number. The A/D module has up to 10

analog inputs, which are multiplexed into one sample

and hold. The output of the sample and hold is the

input into the converter, which generates the result via

successive approximation. The analog reference volt-

ages are software selectable to either the device’s

analog

positive

and

negative

supply

voltages

(AVDD/AVSS), the voltage level on the VREF+

and

VREF- pins, or internal voltage references if available

(VRH, VRL).

The A/D converter has a unique feature of being able to

operate while the device is in SLEEP mode. To operate

in sleep, the A/D conversion clock must be derived from

the A/D’s internal RC oscillator.

The A/D module has four registers. These registers

are:

• A/D Result Register Low ADRESL

• A/D Result Register High ADRESH

• A/D Control Register 0 (ADCON0)

• A/D Control Register 1 (ADCON1)

A device reset forces all registers to their reset state.

This forces the A/D module to be turned off and any

conversion is aborted.

11.1

Control Registers

The ADCON0 register, shown in Figure 11-1, controls

the operation of the A/D module. The ADCON1 regis-

ter, shown in Figure 11-2, configures the functions of

the port pins, the voltage reference configuration and

the result format. The port pins can be configured as

analog inputs or as digital I/O.

The combination of the ADRESH and ADRESL regis-

ters contain the result of the A/D conversion. The reg-

ister pair is referred to as the ADRES register. When

the A/D conversion is complete, the result is loaded

into

ADRES, the GO/DONE bit

(ADCON0<2>) is

cleared, and the A/D interrupt flag ADIF is set. The

block diagram of the A/D module is shown in

Figure 11-3.

FIGURE 11-1: ADCON0 REGISTER (ADDRESS 1Fh).

R/W-0

ADCS1

ADCS0

CHS2

CHS1

CHS0

GO/DONE

CHS3

ADON

R =

Readable bit

W =

Writable bit

- n =

Value at POR reset

bit7

bit 0

bit 7:6

ADCS1:ADCS0: A/D Conversion Clock Select bits

00 = Fosc/2

01 = Fosc/8

10 = Fosc/32

11 = FRC (clock derived from an RC oscillator = 1 MHz max)

bit 5:3,1

CHS3:CHS0: Analog Channel Select bits

0000 = channel 00 (AN0)

0001 = channel 01 (AN1)

0010 = channel 02 (AN2)

0011 = channel 03 (AN3)

0100 = channel 04 (AN4) (Reserved on 28-pin devices, do not use)

0101 = channel 05 (AN5) (Reserved on 28-pin devices, do not use)

0110 = channel 06 (AN6) (Reserved on 28-pin devices, do not use)

0111 = channel 07 (AN7) (Reserved on 28-pin devices, do not use)

1000 = channel 08 (AN8)

1001 = channel 09 (AN9)

1010, 1011, 1100, 1101, 1110,1111 are reserved, do not select.

bit 2:

GO/DONE: A/D Conversion Status bit

1 = A/D conversion cycle in progress. Setting this bit starts an A/D conversion cycle.

This bit is automatically cleared by hardware when the A/D conversion has completed.

0 = A/D conversion completed/not in progress

bit 0:

ADON: A/D On bit

1 = A/D converter module is operating

0 = A/D converter is shutoff and consumes no operating current

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